Digital video streams typically represent video using a sequence of frames or still images. Each frame can include a number of blocks, which in turn may contain information describing the value of color, brightness or other attributes for pixels. The amount of data in a typical video stream is large, and transmission and storage of video can use significant computing or communications resources. Various approaches have been proposed to reduce the amount of data in video streams, including compression and other encoding techniques. These techniques often involve transformation into the frequency domain.